TY  - JOUR
A1  - Leunert, Franziska
A1  - Grossart, Hans-Peter
A1  - Gerhardt, Volkmar
A1  - Eckert, Werner
T1  - Toxicant induced changes on delayed fluorescence decay kinetics of cyanobacteria and green algae a rapid and sensitive biotest
JF  - PLoS one
N2  - Algal tests have developed into routine tools for testing toxicity of pollutants in aquatic environments. Meanwhile, in addition to algal growth rates, an increasing number of fluorescence based methods are used for rapid and sensitive toxicity measures. The present study stresses the suitability of delayed fluorescence (DF) as a promising parameter for biotests. DF is based on the recombination fluorescence at the reaction centre of photosystem II, which is emitted only by photosynthetically active cells. We analyzed the effects of three chemicals (3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), 3,5 Dichlorophenol (3,5 DCP) and copper) on the shape of the DF decay kinetics for potential use in phytoplankton toxicity tests. The short incubation tests were done with four phytoplankton species, with special emphasis on the cyanobacterium Microcystis aeruginosa. All species exhibited a high sensitivity to DCMU, but cyanobacteria were more affected by copper and less by 3,5 DCP than the tested green algae. Analyses of changes in the DF decay curve in response to the added chemicals indicated the feasibility of the DF decay approach as a rapid and sensitive testing tool.
Y1  - 2013
U6  - https://doi.org/10.1371/journal.pone.0063127
SN  - 1932-6203
VL  - 8
IS  - 4
PB  - PLoS
CY  - San Fransisco
ER  - 
TY  - JOUR
A1  - Leunert, Franziska
A1  - Eckert, Werner
A1  - Paul, Andrea
A1  - Gerhardt, Volkmar
A1  - Grossart, Hans-Peter
T1  - Phytoplankton response to UV-generated hydrogen peroxide from natural organic matter
JF  - Journal of plankton research
N2  - In aquatic systems, natural organic matter (NOM) and in particular humic substances effectively absorb the ultraviolet (UV)/visible light spectrum of solar radiation and act as a photoprotective filter for organisms. Simultaneously, UV contributes to the generation of potentially harmful reactive oxygen species (ROS). Dose-response experiments were conducted on cyanobacteria and green algae with hydrogen peroxide (H2O2) as a long-lived representative of ROS. Delayed fluorescence (DF) decay kinetics was used as a non-invasive tool to follow changes of phytoplankton activity in real time. In order to investigate phototoxicity and photoprotection by NOM on phytoplankton, we exposed algae to UV-pre-irradiated NOM and direct UV excitation. Cyanobacteria responded to H2O2 concentrations as low as 10(-7) M, while green algae were 2 orders of magnitude less sensitive. UV irradiation of medium with NOM generated H2O2 concentrations of 1.5 x 10(-7) to 3.6 x 10(-7) M. When exposed to these concentrations, only the DF of cyanobacteria led to a measurable effect while that of green algae did not change. The addition of NOM protected all phytoplankton from direct UV irradiation, but cyanobacteria benefitted less. From this we conclude that UV-irradiated water enriched with NOM can adversely affect the physiology of cyanobacteria, but not of green algae, which might control phytoplankton composition and species-specific activities.
KW  - reactive oxygen species
KW  - Microcystis aeruginosa
KW  - green algae
KW  - delayed fluorescence
KW  - phycocyanin
Y1  - 2014
U6  - https://doi.org/10.1093/plankt/fbt096
SN  - 0142-7873
SN  - 1464-3774
VL  - 36
IS  - 1
SP  - 185
EP  - 197
PB  - Oxford Univ. Press
CY  - Oxford
ER  -